You can use the assets I used, they are from a website I listed in the description of the game’s page. I have two other prototypes that I made myself and a group project here on itch.
And talking about time I found it really helpful to make a small document and/or a trello board to keep track of everything I wanted to do. Also prioritising essential things that the game needs in order to function and then moving on to less and less important parts (look for the MoSCoW method). Hope this helps you too.